1. Field of the Invention
The present invention relates to an internal-combustion-engine automatic stop and restart system that automatically stops an internal combustion engine when a predetermined automatic stopping condition is satisfied while the internal combustion engine is operated, and that restarts the internal combustion engine when a predetermined restarting condition is satisfied while the internal combustion engine is in the automatic stopping mode.
2. Description of the Related Art
In recent years, among internal combustion engines mounted in a vehicle, there has been provided an internal combustion engine in which an internal-combustion-engine automatic stop and restart system (idling stop system) is adopted for the main purpose of reducing fuel consumption. The foregoing internal-combustion-engine automatic stop and restart system is configured in such a way as to automatically stop an internal combustion engine when a predetermined automatic stopping condition is satisfied while the internal combustion engine is operated and to automatically restart the internal combustion engine when the driver performs operation for making the vehicle move and a predetermined restarting condition is satisfied.
By utilizing such an internal-combustion-engine (although referred to also as an engine, it will be referred to as an internal combustion engine herein) automatic stop and restart system, an internal combustion engine that has come into the automatic stopping mode stops while inertially rotating and hence the rotation speed of the internal combustion engine becomes “0”; however, when the internal combustion engine inertially rotates, the internal combustion engine performs the intake stroke, the compression stroke, the power stroke, and the exhaust stroke even under the condition that no fuel is supplied, and the rotation speed of the internal combustion engine fluctuates periodically; then, the periodical fluctuation of the rotation speed causes a vibration.
To date, there has been disclosed a technology (e.g., refer to Japanese Patent Application Laid-Open No. 2007-327365), as a unit for suppressing a vibration caused by the periodical fluctuation in rotation while an internal combustion engine inertially rotates, in which, in order to solve the foregoing problem, the throttle valve provided in the intake pipe is closed until the intake pressure of the internal combustion engine reaches a predetermined pressure and fuel supply is prohibited until the intake pressure becomes the same as or larger than the predetermined pressure.
Moreover, there has been disclosed a technology (e.g., refer to Japanese Patent Application Laid-Open No. 2006-242082) in which the status of an internal combustion engine that has come into the stop mode is estimated and the throttle valve and the like are controlled in accordance with the result of the estimation so that the air-intake amount is changed and hence a vibration is suppressed, and in which, in the case where the rotation speed of the internal combustion engine is the same as or lower than a predetermined speed, the throttle valve is opened and the control amount for the throttle valve is made to vary based on the amount of decrease in the rotation speed of the internal combustion engine.
Furthermore, in the conventional internal-combustion-engine automatic stop and restart system, there has been a problem that, even when the restarting condition is satisfied through the driver's operation of making the vehicle move while the internal combustion engine that has come into the automatic stopping mode inertially rotates, it is difficult to make the pinion gear provided on the starter motor and the ring gear provided in the internal combustion engine engage with each other, because there is produced a rotation-speed difference between the ring gear and the pinion gear, whereby the internal combustion engine cannot be restarted until the rotation of the internal combustion engine stops. There has been disclosed a technology (e.g., refer to Japanese Patent Application Laid-Open No. 2005-113781) in which, in order to solve this problem, the starter motor is rotated in accordance with the rotation fluctuation periodically caused while the internal combustion engine inertially rotates so that the pinion gear is engaged with the ring gear when the rotation-speed difference between the ring gear and the pinion gear becomes small.
In the conventional technology disclosed in Japanese Patent Application Laid-Open No. 2007-327365, fuel supply is kept prohibited until the intake pressure becomes the same as or higher than a predetermined pressure; thus, it is not made possible to restart the internal combustion engine until the intake pressure becomes the same as or higher than the predetermined pressure, even if the driver performs operation of making the vehicle move while the internal combustion engine inertially rotates. Accordingly, the delay of restarting hinders the driver from making the vehicle move as he likes, whereby the driver may sense discomfort.
In the conventional technology disclosed in Japanese Patent Application Laid-Open No. 2006-242082, the throttle valve is controlled even after the internal combustion engine has stopped; therefore, electric power may be consumed wastefully. Furthermore, the control amount for the throttle valve is changed in accordance with the amount of decrease in the rotation speed of the internal combustion engine; thus, there may be caused a combustion failure, because, when there exists a restart request after the control amount for the throttle valve has been changed, the amount of air becomes too much or too small.
In addition, in the conventional technology disclosed in Japanese Patent Application Laid-Open No. 2005-113781, in the case where the fluctuation in the rotation speed of the internal combustion engine is large or the amount of decrease in the rotation speed is large, the control of the starter motor cannot keep up with the change in the rotation speed of the internal combustion engine; therefore, it may become impossible to restart the internal combustion engine while the internal combustion engine inertially rotates, because there continues the state where it is difficult for the pinion gear and the ring gear to engage with each other. Furthermore, in the conventional technology disclosed in Japanese Patent Application Laid-Open No. 2005-113781, the starter motor is rotated in accordance with the periodic rotation fluctuation caused while the internal combustion engine inertially rotates; therefore, there exists a problem that the calculation load on the internal combustion unit becomes large, because it is required that, taking the characteristics such as the responsiveness of the starter motor into account, there is performed control of the starter motor in accordance with each of the intake stroke, the compression stroke, the power stroke, and the exhaust stroke.